Immunity & Vaccines 8/29/25

Vocabulary flashcards covering foundational immune concepts, vaccine types, and safety considerations from the notes.

Innate immunity

The non-specific, immediate first line of defense that acts without prior exposure, including skin/mucosa barriers, cells (neutrophils, macrophages, dendritic cells, NK cells), and soluble factors (complement, cytokines).

Adaptive immunity

The specific, delayed but memory-forming immune response involving B lymphocytes (antibody production) and T lymphocytes (helper and cytotoxic) that provides long-term protection.

Why does a kid only get chickenpox once?

Primary infection of varicella zoster virus. B cells make virus specific antibodies and T cells make cytotoxic memory cells.

After recovery the memory exists for life. If exposure happens again, the memory fights off virus before illness occurs.

Immunosuppression can allow reactivation later in life (shingles)

B lymphocytes

Adaptive immune cells that differentiate into plasma cells to produce antibodies against pathogens.

T lymphocytes

Adaptive immune cells that include helper T cells (coordinate responses) and cytotoxic T cells (kill infected cells).

Antibodies

Proteins produced by B cells (immunoglobulins) that bind antigens to neutralize pathogens or mark them for attack.

Memory cells

Long-lived B and T cells that persist after infection or vaccination, enabling faster responses on re-exposure.

Vaccine

Biological preparation that stimulates immunity to prevent severe complications of disease by training the adaptive immune system; not a treatment.

Active immunity

Immunity developed through infection or vaccination, resulting in memory B/T cells and long-lasting protection.

Passive immunity

Immunity provided by ready-made antibodies from another source, offering immediate but temporary/short term protection with no memory. (placenta, ivig, antitoxin)

Herd immunity

Protection of non-immune individuals when a critical portion of the population is immune, reducing disease transmission.

Threshold varies by disease.

Booster

Additional vaccine dose given after the initial series to sustain or enhance immunity and prevent waning.

Conjugated vaccine

Vaccine where a polysaccharide antigen is linked to a protein carrier to evoke T-cell help and improve memory, especially in infants less than 2 years old.

Polysaccharide antigen

A sugar-based bacterial capsule component used as an antigen; often elicits a weaker, T-independent response in young children.

Protein carrier

A protein linked to a polysaccharide to convert a T-cell independent response into a T-cell dependent one.

Hib vaccine

Haemophilus influenzae type b conjugate vaccine; dramatically reduced Hib meningitis by improving immune memory.

PCV13

Pneumococcal conjugate vaccine covering 13 serotypes; an example of a conjugated vaccine.

MenACWY

Meningococcal conjugate vaccine protecting against serogroups A, C, W, and Y.

MMR vaccine

Vaccine protecting against measles, mumps, and rubella; example of a live-attenuated vaccine.

Live-attenuated vaccine

Vaccine using a weakened form of the pathogen that can replicate; often long-lasting immunity but contraindicated in pregnancy and some immunocompromised individuals.

Inactivated (killed) vaccine

Vaccine using whole pathogens that have been killed; cannot replicate but may require boosters and adjuvants.

Subunit/recombinant vaccine

Vaccine using specific antigen fragments or recombinant proteins to stimulate immunity; often needs boosters.

Toxoid

Inactivated bacterial toxin used as a vaccine to protect against toxin-mediated diseases (e.g., diphtheria, tetanus).

mRNA vaccine

Vaccine delivering mRNA encoding an antigen; host cells produce the antigen, eliciting an immune response.

Viral vector vaccine

Vaccine using a harmless virus to deliver an antigen gene into host cells to provoke immunity.

Monoclonal antibodies (mAbs)

Lab-engineered antibodies providing passive immunity by targeting specific antigens; no memory and temporary protection.

Immunization schedule

Recommended timing and dosing of vaccines across ages (adult and pediatric schedules).

Vaccination safety surveillance (VAERS)

Vaccine Adverse Event Reporting System in the U.S. used to monitor vaccine safety signals.

True Contraindication

A situation where a vaccine should not be given (e.g., severe allergic reaction, certain live vaccines in pregnancy (MMR, varicella, intranasal flu) or immunocompromised).

Precaution

A condition in which vaccination may be delayed or considered carefully; not an absolute contraindication.

When already fighting moderate/severe acute illness. Recent recipient of antibody containing blood product (blood transfusion w/ antibodies, etc)

Not contraindications (myths)

mild illness, antibiotic use, family history of adverse reaction

Adverse effects

Reactions to vaccines: common local/systemic (pain, mild fever, fatigue, muscle pain); rare serious events (anaphylaxis, GBS, febrile seizures, intussusception, etc.).

VAERS

vaccine adverse event reporting system (in USA)

literally anything can be reported :(

Immunocompromised

Weakened immune system due to disease or treatment; influences vaccine choice and timing (often avoiding live vaccines).

• Avoid live vaccines (chemo, rituximab, transplant, HIV with low CD4)

• May need additional doses or timing adjustments

Shingrix (RZV)

Recombinant zoster vaccine; adjuvanted subunit vaccine for herpes zoster used in older adults.

RSV mAb (Nirsevimab)

Monoclonal antibody given to infants to provide passive protection against respiratory syncytial virus.

Immunologic memory

The ability of the immune system to respond more rapidly and effectively on future exposures after initial activation.

Infants and young children

Special population.

• Immature immune systems → require conjugated vaccines

• Multiple-dose series to build memory

Elderly over 65

Special populations

Immune senescence → higher-dose or adjuvanted vaccines (e.g., high-dose influenza, Shingrix)

Pregnancy

Special population

• Safe & recommended: Tdap (3rd trimester), influenza

• Contraindicated: live vaccines (MMR, varicella, intranasal flu)

monoclonal antibodies (mABs)

Lab engineered antibodies targeting specific antigens.

Advantage is their specificity (precision medicine)

Produced by cloned B cells in lab. Provide passive immunity since your body doesn’t have to do anything to get that immunity. Temporary, NO MEMORY

Used in oncology, autoimmune disease, allergies, infectious disease

mABs vs vaccines

passive vs active immunity

limitations to monoclonal antibodies

possible adverse effects

practical barriers: expensive, infusion admin, monitoring required

only temporary infection, no memory and possible need to reinfuse

access issues: insurance approval, availability